Fill a large pan with water, season with salt and bring to a boil. Fill a large bowl with ice water. Drop the asparagus in the boiling water and cook until just tender, about 4 minutes, then lift out the spears and plunge them in the ice water. Once cool, dry the asparagus on tea towels.

Boil water again and drop in the egg. Cook for 9 minutes, then let it cool before peeling it.

Arrange the asparagus on a platter. Sprinkle on the olive oil, and squeeze over a little lemon juice. Place the egg in a sieve and use the back of a spoon to mash it through the sieve and over the asparagus. (Hence the name -- the fluffy yellow-and-white sieved egg resembles mimosa flowers.) Finish the dish with a coarse grind of pepper and a dash of salt.